UV400 means the lenses block all ultraviolet light with wavelengths up to 400 nanometers. That covers both UVA and UVB rays, the two types of UV that reach the earth. In practice, UV400 is the same as “100% UV protection.”
UVA, UVB and Why 400
Sunlight contains three types of ultraviolet light:
- UVB (280 to 315 nm) is the strongest and causes sunburn, also on the eyes.
- UVA (315 to 400 nm) reaches deeper and is present all day, all year.
- UVC (below 280 nm) is absorbed by the ozone layer and doesn’t reach us.
Because UVA ends at 400 nm, a lens that blocks everything up to 400 nm blocks all the UV that matters.
Why UV Protection Matters
Over the years, UV exposure is linked to cataracts, growths on the eye’s surface and damage to the delicate skin around the eyes. In the short term, intense light on snow or water can cause a painful, sunburn-like irritation of the eye. The effect builds up slowly, which is why everyday protection matters more than the occasional beach day.
Darker Doesn’t Mean Safer
How dark a lens looks says nothing about its UV protection. Darkness and UV filtering are two separate things.
- A dark lens without UV protection can be worse than none at all. Your pupils open wider behind the tint, letting in more UV.
- A light or colored lens can still be fully UV400.
Darkness is measured separately, in filter categories from 0 (almost clear) to 4 (very dark). Category 3 is the most common for bright, sunny days. Category 4 is too dark for driving.
How to Check Your Sunglasses
- Look for UV400 or 100% UV protection on the label, the product page or the inside of the temple.
- In Europe, look for the CE mark, which means the lenses meet the European standard for sunglasses.
- Not sure? Many opticians can test your lenses with a UV meter in seconds.
Home tricks, like shining a flashlight or a banknote checker through the lens, aren’t reliable.
Quick Answers
Is UV400 the same as polarized?
No. UV400 is about invisible UV light. Polarization reduces visible glare from water and roads. A lens can have one without the other. More on that in polarized vs non-polarized sunglasses.
Do I need UV protection on cloudy days?
Yes. Most UV passes through clouds, and snow, sand and water reflect it back up.
Does lens color affect UV protection?
No. Gray, brown, green or pink can all be UV400. Color changes how you see, not how well you’re protected. See our lens color guide.
Our Lenses
Every Club Marbs frame comes with UV400 lenses, set in acetate frames. Browse the full collection.
Keep reading: Acetate vs plastic sunglasses · How to clean and care for your sunglasses
